Magnet design



L.. M. KEEFE MAGNET DESIGN Aug. 4, 1942.

Filed Dec. l1, 1940 Irisa/a fiar;

INVENTOR 12217200311, Mjf

41AM #glw ATTORNEYS Patented Aug. 4, 1942 UNITED STATES PATENT OFFICEMAGNET DESIGN Lincoln M. Keefe, Springfield, Mass.

Application December 11, 194.0, Serial No. 369,567

(Cl. 17E-336) 6 Claims.

This invention relates to improvements in magnet design and has for anobject the provision of electro-magnets in which the average air gapbetween the movable armature and the stationary head when the armatureis positioned to be attracted when the electro-magnetic winding isenergized, is a minimum as compared to conventional types.

Another obj ect ofthe invention is the provision, in an electro-magnet,of magnetizable heads which together with a magnetizable tube and thearmature completely enclose the electro-magnetic winding and define apath for the lines of force set up in the core of the electromagnet whenits winding is energized.

A further object is to form an opening in one of said magnetizable headsand pivotally mount in this opening an armature of substantially thesame thickness as that of the head. The air gap between the outer edgesof the armature and the inner edges of the opening is substantiallyuniform and Varies Very slightly from the open to the closed (orattracted) positions.

Yet another object of the invention is the provision of serrations onthe inner face of the armature, and in other instances of serrations onthe core head adjacent to the armature. These serrationsv maybecircumferential or of any other desired form, and serve as iluxintensiilers. When the winding is energized an intense fringe or brushof ilux extends from each serration, producing a magnetic fieldcomprised of a series of zones in which the magnetic ux is intensifiedwith zones in which the flux is of less intensity therebetween.

Another object of the invention is the provision of an electro-magnetfor actuating switching means or for instituting mechanical movement,formed of parts which fit together in accurate relation and may bepermanently secured together without the necessity for fasteningmembers, thereby producing a, device of the maximum accuracy at aminimum of cost. Devices of this form may be grouped in close order, dueto the symmetry thereof, and therefore space is saved in the mechanismsin which these devices are employed.

Other objects will be apparent to those familiar with the art in whichelectro-magnets, relays and the like fall.

Referring to the drawing:

Figure 1 is an elevation of my new and improved electro-magnet device;

Figure 2 is a sectional elevation of the electromagnet taken along theline 2-2 of Figure 1;

Figure 3 is a plan view showing details of the armature and the methodof mounting it;

Figure 4 is a view of the magnet in Figure 1, as seen from the bottomlooking upwardly; and

Figure 5 is a sectional view taken along the line 5-5 of Figure 2, andshowing serrations formed in the surface of the armature.

Referring to the drawing, the magnet, generally designated by thenumeral I0 includes a core II having reduced portions at each endthereof, one of which is designated by the numeral I2, formingshoulders. Heads I3 and I4 formed of insulation material rest upon theshoulders. A disk I5 formed of magnetizable material has a hole formedtherein fitting the portion I2 of the core II. After the head I3 and thedisk i5 are placed on the core the end of the core is riveted down topermanently secure the head and the disk thereon.

A similar disk i5 is mounted on the opposite end of the core and saidend is riveted down to secure this disk and the head I4 thereon.

The lower end, as viewed in Figure 2 of the core, has a tapped hole Ilformed therein. This hole may be engaged by a threaded stud on thewinding machine for applying the windings I8 to the core. suitableleadout wiresV I9 and 2l);`-

Secured to the core by means of a screw 2| engaging the threaded hole Ilis a comparatively thick head 22 of iron or other ferrous material. Thehole formed in the head 22 for the passage of the screwr2| iscountersunk so that the head of the screw is flush with the outersurface of the head. The head 22 also has formed therein holes carryingbushings 23 and 23a through which the leadout Wires I9 and 20 pass. Thehead 22 also has beveled flat portions 24, 25 and 26.

A sleeve member 21 also formed of iron or other ferrous material hasstruck-out portions forming ears 28 and 29 having holes 30, 3|respectively formed therein to accommodate mounting screws. The shellhas a counterbored portion 32 at one end thereof forming a press litwith the head 22 and a counterbored portion 33 forming `\a press t witha head 34.

The head 34 is similar to the head 22 in so far as thickness isconcerned. However, it has an opening formed therein to accommodate anarmature. 'I'he opening has a portion 35 which is circular andconcentric with the outer diameter of the head 34. The opening has ilatportions 36 and 31 and a slotted portion 38. A hole 39 extends throughthe head at right angles to The windings are provided withVV and passingthrough the slot 33 (see Figure 3).

Referring now to Figure 2, an amature 4I has a tongue portion 4I whichnts the slot 38, and a pivot pin 42 is mounted in the hole 39 and passesthrough the corresponding hole in alignment therewith in the tongue 4I.'I'he head 34 is also provided with beveled flat portions 43, 44 and 45.

In assembling the electro-magnetic device, the head 22 is secured to thecore II by means of the screw 2I and this assembly is pushed into thetubular shell 21 until the head 22 is flush with the lower end of thetube. In so doing, the head 22 comes to rest against the shoulder 32a.I'hen the head 34, the armature 40 having been previously pivotallymounted therein, is pressed into the upper end of the tube until thehead 34 comes to rest against the shoulder 33a.

The heads 22 and 34 are then retained in positlon against the shoulders32a. and 33a respectively by deforming the tubular shell and causingportions thereof to overlie the beveled flat portions 24, 25, 26 and 43,44, 45 respectively.

The armature 40 may be provided with any suitable type of extension inaccordance with the instrumentalities it is desired to control with thedevice herein shown and described. In one use of the device, forexample. a positionable member is to be controlled; an arm 46 ispreferably formed integral with the armature 40. This arm may have aportion milled away forming a shoulder 41, and a face 48 on the web 49.The web 49 may have a tapped hole 50 formed therein. Suitable meansconnecting the arm 46 to the positionable device (not shown) may beprovided and may be secured to the web 49 by means of a screw engagingthe threads 50 and located by means of the shoulder 41. Suitable springmeans may be associated with the positionable member or with the meansconnecting the same to the arms 46, for urging the armature 40 away fromthe core II and the disk I5. A suitable notch formed in the arm 46 comesto rest against the head 34 and serves as a stop for limiting the upwardswing of the armature 40.

In other uses of the device, spring means for urging the armature awayfrom the core may be carried on the head 34 or on the tubular shell 21;for example, a cotter pin 52 may be secured to the arm 46 in the mannershown, and the shell 21 may have an ear 53 extended outwardly in amanner similar to the ears 28 and 23, and the spring 54 may have one endconnected to the ear 53 and the other end connected to the cotter pin52.

The armature 40 may be provided with a nonferrous rivet 51 to preventthe armature from coming in metallic contact with the disk I5 and theend of the core II and sticking The surface of the armature 40 facingthe core II may be provided with serrations 55 which may be disposed inthe surface in any desired form. For example, the serrations 55 may becomprised of a plurality of concentric grooves.

In the embodiment herein shown and described, the surfaces of thegrooves or serrations are at an angle of 60 with the horizontal. Thereare eighty serrations per inch and the depth of each groove is .008".

The disk I5 may also have its surface facing the armature 40 providedwith serrations 50. In the embodiment illustrated this disk may have 60serrations, eighty to the inch and .008" deep.

By providing the magnet with a serrated area I4 and the amature with theserrated area 55. the action of the device when the winding Is energizedis facilitated due to the fact that the magnetic flux forms concentratedfringes on the peaks of these serrations and thereby provides a seriesof concentrated annuli with areas less concentrated therebetween.

From tests made with this new and improved magnetic device, it has beenfound that the device will operate unfailingly on electrical impulses ofvery short duration passing through the windings, therefore it is fastacting. Furthermore, it will operate under the influence of longer livedimpulses of greatly reduced current value and is therefore believed tobe very efficient.

Although a single embodiment of the new and improved electro-magneticdevice is herein shown and described, it is obvious that many changesmay be made in the device without departing from the spirit of theinvention as set forth in the annexed claims.

What is claimed is:

1. In an electro-magnetic device, a permeable magnetic core, a windingon said core, permeable magnetic heads at each end of said core, one ofsaid heads having an opening formed therein, an armature mounted in saidopening, a pin passing through said last head and pivotally engagingsaid armature, a permeable magnetic sleeve joining said heads embracingsaid winding and forming a return path for the magnetic flux generatedin said core, said sleeve covering the ends of said pin and confiningthe same in said last head, and means on said armature and movabletherewith for controlling a positionable device.

2. In an electro-magnetic device, a core, a winding carried on saidcore, permeable magnetic members carried on each end of said core, saidmembers being larger in diameter than the diameter of the core,permeable magnetic heads at each end of said core, said heads beingadjacent to said members and one of said heads having an opening formedtherein, an armature mounted in said opening and adapted to be attractedby flux distributed over the surface of one of said members, a pinpositioned in said head and forming a pivotal support for said armature,a permeable magnetic sleeve forming with said heads a housing for saidcore and said winding and forming a return path for the magnetic flux insaid core, said sleeve also serving to retain said pin in said lasthead, and means carried on said armature and movable therewith.

3. In an electro-magnetic device, a core having insulating heads at eachend thereof, a winding on said core between said insulating heads,permeable magnetic members carried on each end of said core and adjacentto said insulating heads, said members being larger in diameter than thediameter of said core, a permeable magnetic head in contact with one ofsaid members at one end of said core, a second permeable magnetic headadjacent to the other of said members and having an opening formedtherein of an area larger than the area of said last mentioned member,an armature positioned in said opening in said last mentioned head, saidarmature being adapted to be attracted by flux distributed over thesurface of said last mentioned member, a pivot pin in said last headforming a pivotal support for said armature, a permeable magnetic tubeforming with said heads a housing for said core and said winding,forming a return path for the magnetic flux generated in said core andserving as a retainer for retaining said pin in said head, and meanscarried on said armature for connection to movable means outside saiddevice.

4. An electro-magnetic device according to claim 3 in which said sleevehas integral portions of its wall remote from the ends of said sleeveextending outwardly and forming lugs for mounting said device.

5. In an electro-magnetic device, a permeable magnetic core, a windingon said core, permeable magnetic heads at each end of said core, one ofsaid heads having an opening formed therein, an armature mounted in saidopening, a pin passing through said last head and-pivotally engagingsaid armature, a permeable magnetic sleeve joining said heads togetherand embracing said winding, said sleeve being adapted to form a returnpath for the magnetic ux generated in said core and also covering theends of said pin and confining the same in said last head, said corehaving a free end spaced apart from said armature and the surface ofsaid free end of said core being serrated to present a. plurality ofmagnetic fringes toward said armature, and means on said armature andmovable therewith for controlling a positionable device.

6. In an electro-magnetic device, a core, insulating heads on each endthereof, a winding on said core, permeable magnetic members carried oneach end of said core, said members being larger in diameter than thediameter of said core and backing up said insulating heads, permeablemagnetic heads at each end of said core, one of said heads being incontact with one end of said core, and the other of said heads having anopening formed therein, said Opening being generally circular in formand terminating in an inwardly directed slot formed therein, an armaturemounted in said opening similar in shape to the shape of said openingand having a tongue portion lying in said slot, a pin in said headextending through said tongue portion and said slot for pivotally suD-porting said armature in said last head, a permeable magnetic tubeforming with said heads a housing for the core and its winding andforming a return path for the magnetic flux, said tube also serving toretain said pin in said last head, the other end of said core beingslightly spaced apart from said armature and forming a free pole, aplurality of serrations formed in the surface of said pole, a pluralityof other serrations formed in the surface of said armature facing saidpole, and means on said armature and movable therewith controlling apositionable member external to said device.

LINCOLN M. KEEFE.

